1) To determine the pharmacokinetics of orally administered vs intravenous methylprednisolone in pediatric vasculitis (standardized at 50mg/M2). 2) To determine if impaired D-xylose absorption is correlated with markers of vasculitis (neopterin, vWfAg) and decreased absorption when oral drug is compared with IV drug. 3) To determine whether impaired D-xylose absorption improves with control of disease activity.